Ford Explorer 2006 is shaking / vibrating after I changed Spark Plugs

My Ford Explorer 2006 is shaking / vibrating after I changed all 6 Spark Plugs at mechanic. Vibration is clearly felt at idle or slow speed. what can be problem, any solutions. I computer checked engine at form mechanic, diagnosed OK.

If a mechanic changed your plugs, bring it back. Possible causes are a plug not gapped correctly, or a plug wire not returned to the proper location. If it was running correctly before, it should not be running bad after replacing the plugs

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